+my @chars2 = (['_'], @chars); # trailing character (extended set)
+my @columns = !exists $get{split} ? \@chars2 :
+ ([@chars2[0, 1, 3, 4, 6]], [@chars2[2, 5, 7]]);
+
+if ($mode) {
+ my $xorg = do 'data/digraphs-xorg.inc.pl'
+ or die "Error loading Xorg data: ", $@ // $!;
+ $_ = [ord $_] for values %{$xorg};
+ $xorg->{$_}->[2] = # class = compatibility
+ $di->{$_} ? $di->{$_}->[0] != $xorg->{$_}->[0] ? 'l1' : # conflict
+ $di->{$_}->[2] =~ /\bu-di\b/ ? 'l5' : 'l3' : 'l2' # rfc|any|none
+ for keys %{$xorg};
+
+ for my $cp (map {$_->[0]} values %{$xorg}) {
+ next if (state $seen = {})->{$cp}++; # List::MoreUtils::uniq
+
+ # find multiple equivalent mnemonics
+ my @equiv = grep {$cp eq $_->[0]}
+ map {$xorg->{$_}} sort keys %{$xorg}; # values ordered by mnem.